Plasma jet engine



l U *l l FI :D85 U NOV- 2, 1965 G. N. HATsoPoULos ETAL 3,215,869

PLASMA JET ENGINE Filed Dec. 51, 1959 NOV- 2, 1965 G. N. HATsoPouLos ETAL 3,215,859

PLASMA JET ENGINE 3 Sheets-Shea?l 2 Filed Deo. 31, 1959 NUV- 2, 1965 G. N. HATsoPouLos ETAL 3,215,859

PLASMA JET ENGINE United States Patent O 3,215,869 PLASMA JET ENGINE George N. Hatsopoulos, Lexington, and Eustratios N.

Carabateas, Boston, Mass., assignors to Thermo Electron Engineering Corporation, a corporation of Delaware Filed Dec. 31, 1959, Ser. No. 863,220 8 Claims. (Cl. 310-11) This invention relates to processes and apparatus for converting thermal energy into electrical energy, and more particularly to processes and apparatus which do not require any moving mechanical parts for effecting such conversion.

It is well known to convert heat into electricity by conventional turbogenerators. However, it has become desirable, especially in processes for the utilization of nuclear energy, to convert thermal to electrical energy by processes and apparatus which do not require any mechanical moving parts yet result in high current and power densities and exhibit high coefficients of performance. Thermo-electric generators, thermionic converters and gaseous thermocouples are but a few of the sys-tems which have been subjected to recent study. Additionally, attempts have been made to effect the direct transformation of the kinetic energy of an ionized gas into electricity by passing a plasma jet through a magnetic field and collecting the ion current produced.

In plasma jet engines previously proposed, a gas has been generated at high temperatures and pressures and expanded adiabatically through a nozzle into a chamber where high gas velocities and low pressures are produced. Ionization of the gaseous molecules has ben effected by electron emission into the ionization chamber from heated cathodes, electric arcs or by submission of the enclosed gases to the influence of X-rays. An external magnetic field has then been applied transverse to the direction of fiow of the space charge neutralized ionized gas (plasma), which field serves to deflect the charged ions present in the plasma toward electrodes positioned. within the enclosed chamber. In order to obtain an output current, it has been necessary, due to the presence of positive ion sheaths surrounding each electrode, which make the electrodes negative with respect to the plasma, to match the electrodes with the plasma. To this end, thermionic cathodes have been employed to produce electron currents and to reduce the cathode surface resistance.

The strong magnetic field utilized in known plasma jet engines has impaired current and power outputs of such devices. Such magnetic field is formed parallel to the surfaces of the electrodes and acts to cut off both the random ion current from the plasma to the electrodes and the electron current produced by the thermionic cathode. Heretofore, plasma jet engines have accordingly been capable of only negligible current and negligible power outputs.

Additionally, the internally placed ionizing means known to the prior art have presented interference with the gas flow and have decreased the efliciency of energy conversion. In many cases, use of the heated cathodes, electric arcs or the like of the prior art has resulted in 'charge loss to the duct walls and negligible ionization of the plasma in the ionization chamber.

It is an object of the present invention to provide a process and apparatus for the conversion of the energy of a plasma to electrical energy without the utilization of any mechanical moving parts and with the production of high thermal efiiciencies and higher current and power outputs than those heretofore obtained.

Another object of this invention is to provide a process and apparatus for the conversion of the energy of a plas-ma to electrical energy wherein an oriented magnetic ice field is applied to the ionized particles of the plasma, which field does not interfere with the collection of electrical energy.

It is a further object of the present invention to provide a process and apparatus for the conversion of the energy of a plasma to electrical energy wherein the ionization of the plasma is effected without interference with gas flow or objectionable change leakage to the system surroundings.

It is still another object of the present invention to provide a plasma jet engine in which the proper correlation is obtained between the electrode dimensions, the velocity of the plasma stream, fractional ionization, temperature of the gas, and the strength of the magnetic field to give satisfactory current efficiencies.

The proces of our invention involves the isentropic expansion of a fluid, the ionization of the Huid, the application of a magnetic field normal to the direction of fluid flow to produce a plasma wherein a random ion current is present, the production of electron flow through the plasma and the collection of the resulting currents while simultaneously orienting the magnetic lines of force to eliminate magnetic interference with the output current produced. Surprisingly, we have discovered that magnetic interference with the generation of electric current in plasma jet devices is eliminated and high current and power outputs are obtainedl by following this procedure.

The apparatus for practicing the invention comprises means providing a source of an ionizable fluid at high temperatures and pressures, a nozzle for the isentropic expansion of the fluid, an expansion chamber in which a plasma is formed, an ionizing means for the fluid, means for creating a magnetic field in the chamber and a pair of collector electrodes positioned within the charn- Iber which are composed of a magnetic material or are suitable magnetically shielded for orienting the magnetic eld perpendicular to the electrode surfaces. Preferably, the ionizing means of the present invention comprises a high frequency power supply positioned external to the expansion chamber for producing an electric field in the chamber to ionize the moving plasma without interfering with plasma fiow or producing charge loss to the Walls of the apparatus.

Further objects and advantages of the present invention will be apparent from reference to the following detailed description taken in connection with the accompanying drawings disclosing, for purposes of illustration without limitation, preferred embodiments of this invention wherein:

FIGURE 1 shows a schematic perspective representation of one embodiment of the plasma jet engine;

FIGURE 2 shows a schematic perspective representation of .another embodiment of the plasma jet engine, utilizing an ionizing means differing `from that depicted in FIGURE 1;

FIGURE 3 shows an enlarged perspective view, partially in section, of a portion of the expansion chamber 17 of FIGURES 1 and 2;

FIGURE 4 is a diagrammatic vertical section taken along the line 4 4 of FIGURE 3, illustrating the magnetic field orientation of the present invention;

FIGURE 5 is a View similar to FIGURE 4, showing the magnetic lines of force in expansion chamber 17, in the absence of all magnetic shielding; and

FIGURE 6 is a plot showing the relationship between the Mach numbers of the plasma stream plotted as abscissae and the dimensionless distance D plotted as ordinates; las will be explained more fully hereinafter the dimensionless distance D is a value employed in defining the correlation or relationship between the parameters of the conditions of operation of the plasma jet engine which gives satisfactory efficiencies.

Referring to FIGURE 1, an embodiment of the device of this invention is shown wherein a working fluid is circulated in a closed cycle from a boiler 11 where it is heated, through a nozzle 15 where adiabatic expansion occurs, into an expansion chamber 117 where the energy of the plasma -created is converted to electric current, out to a condenser 19 where the fluid is cooled and condensed and is thereafter recycled to the boiler 11 by means of a pump 21.

The working fluid employed is an ionizable vapor or gas which has a l-ow ionization potential, i.e., from about 3.9 to 10 electron volts. Materials suitable for use as Working fluids in the plasma jet engine of this invention include mercury, sodium, ces'ium, lithium and potassium.

ACondensation after the ladiabatic expansion through the nozzle 115 should be avoided for smooth operation. The pressure in expansion chamber 17 is therefore maintained below the vapor saturation pressure corresponding to the temperature within chamber 1-7.

For large installations it is advantageous t-o use supersonic flow; the greater the Mach number M l Velocity of Working fluid Velocity of sound the better. yIn FIGURE 1 of the drawing, M1 indicates the Mach number of the working iiuid at the entrance end of the magnetic field within expansion chamber 17 and M2 the Mach number of this fluid at the exit end of this magnetic field. This invention comprehends operations with working fluid flows h-aving Mach numbers up to 10. For smaller installations subsonic flow (having Mach numbers less than 1) can be employed, if desired, but even in such installations ysupersonic liows are preferred.

The Mach number M is dependent -on the vapor temperature and pres-sure of the working fluid :at the point it enters nozzle 1'5, i.e., the stagnation temperature and pressure respectively. Stagnation temperatures Aof the rder of from \1600 K. to =2400 K. with the working fluids hereinabove disclosed give Mach numbers of the |order of 3 or 4; higher temperatures result in greater Mach numbers.

In general, stagnation temperatures of from about 900 K. to 3000 K. are used; the preferred range is from 1000 K. to '2200J K. Stagnation pressures range from Iabout 0.1 atmosphere to 5 atmosphere-s; the preferred range is from 0.1 atmosphere to 1 atmosphere.

When the Mach number M1 is less than 1, then the value of M2 cannot exceed 1. When, on the other hand, the Mach number M1 is above 1, say 110 or less, the Mach number of the Working uid at the exit end of the magnetic 4field c-an be reduced to a lower value but not below 1 (see One Dimensional Flow l.of Ionized Gases Through a Magnetic Field, Patrick et al., Journal of Fluid Mechanics, 289-309, February 1959). For 'any given value of M1, the closer the Mach number M2 is to unity, the greater is the c-onversion of the thermal energy iof the plasma to electrical energy.

The heated gas is accelerated through the nozzle into the expansion chamber 17, where means 'are provided to ionize the fluid. *In the -embodiment of FIGUR'E 1, an external high frequency power supply -23 is connected through suitable leads 25 to a pair of ionizing electrodes 27 fabricated `from any flexible conductor in the form of continuous .bands surrounding the ioniz-ation chamber. The power supply 2'3 may operate from the output voltage of the plasma jet generator or from :an external source, as convenient. The electrodes create a high frequency electric field within the chamber 17, thereby ionizing the ionizable fluid and producing a plasma moving at high velocities. The use of an external high frequency ionization source creates no interference with the plasma liow and minimizes charge loss t-o the duct Walls of the ionization chamber 17. The high frequency Power source may operate at various frequencies dependent upon the working fluid pressure and the intensity of the magnetic field imposed upon the moving plasma. Frequencies of from kilocycles to 10,000 megacycles may lbe employed; the preferred frequency range is `from `1,000 kilocycles to 1,000 mega-cycles.

:Frequencies should be employed, or the gals ionized thermally 'as described hereinafter, to effect a fractional ionization Iof the flowing plasma lof from 0.01% t-o 10% of the number Iof neutral plasma particle-s, preferably from about 0.1% to 1%.

It will 'be noted that in the embodiment tof FIGURE 1, ionization -of the working Kfluid takes place in the magnetic field within expansion chamber -17 where conversion of thermal energy into electrical energy is effected. By ionizing the working fluid within the magnetic Ifield, maximum utiliz-ation of the ionized particles in obtaining current output is effected.

In the embodiment of FIGURE 2, an alternative means for ionizing the flowing fluid is illustrated. In FIGURE 2, the liuid circulated through boiler 11 passes through a superheater 13 positioned in advance =of the expansion chamber 117. The liuids are thermally ionized within the superheater and expand through nozzle -15 in the `form of 'an -ionized plasma. The thermal ionization achieved with cesium vapors, for example, is equal 'at 2,000 K., t-o 0.32% at a pressure of 1 mm. and 0.065% at at pressure of 5 m-m., and increases to 3.2% at a pressure rof 1 mm. and 0.65% at a pressure of y5 mm. when the exit temperature from the superheater is increased to v2,500 K.

Whether ionization is effected by the means illustrated Iin either FIGURE 1 or 2, the vaporized fluid flows through the orifice |of nozzle 15 intro the expansion chamber I17'. The lfluid, which now may be termed a space charge neutralized ionized gas or plasma, is `subjected to a :strong magnetic field produced by the magnet 29, which surrounds the expansion chamber. Either a permanent or eelctromagnet may -be employed, as desired. The -rnagnetic field lserves to delle-ct the charged particles comprising a random i-on current toward either of the electrodes 31 or 41 (seen in FIGURE 3) for -current collection. The magnetic field may range from 5 103 gauss to y5 104 g-auss; the preferred field strength may be 5 103 to 2 l104 gauss.

Referring now to FIGURE 3, the structure of the expansion chamber 17 may be more clearly seen. A plasma moves through such chamber at a velocity normal to the magnetic flux (E) impinged thereon. At opposite walls of the expansion chamber are electrodes 31 and 41. The electrodes, which are positioned within chamber 17 at opposite sides thereof, are insulated from the walls of the chamber and connected by suitably insulated leads passing through conventional vacuum seals to external circuits.

The thermionic cathode 31 preferably comprises an electron emitter 34 heated indirectly as by the passage of current through leads 32 to resistances 33 or by some other conventional means, such as by direct current heating, by passing a hot gas in heat exchange therewith or by placing radioactive isotopes in heat exchange relation therewith. If radioactive isotopes are used, suitable shielding will, of course, be required. The electron emitter may be:

(1) A Philips cathode, either A or B type, which is sintered porous tungsten impregnated with various oxides, usually in the form of carbonates, which carbonates upon activation are converted to oxides; Type A cathodes contain barium oxide and aluminum oxide in the mol ratio of five to two. Type B cathodes contain barium oxide,

aluminum oxide and calcium oxide in the mol ratio of five to two to three;

(2) Thoriated tungsten or thoriated molybdenum; (3) Tungsten coated with cesium;

(4) Thoria, i.e., ceramic T1102;

(5) Barium oxide, strontium oxide, calcium oxide, and mixtures of these oxides;

(6) Molybdenum housing or stocking filled with granules of a fused barium oxide and aluminum oxide mixture;

(7) Lanthanum oxide (La203);

(8) Perforated molybdenum sleeve or housing containing sintered thorium oxide; and

(9) Pure tungsten.

While any type of good electron emitter may be used, it is preferred that the electron emitter be prepared from thoriated tungsten or thoriated molybdenum.

The electon emitter 34 is provided with magnetic shielding which comprises the walls of electrode 31 and forms a casing into which resistances 33 and electron emitter 34 may be molded or otherwise formed. Inasmuch as it is important that the magnetic shielding retain its ferromagnetic properties at the high operating temperatures utilized in the plasma jet engine, those materials utilized for the shielding have high magnetic transition temperatures (Curie points). Among the materials found suitable for the cathode magnetic shielding are cobalt metal, whose Curie point is l400 K.; Permendur, an alloy consisting essentially of 50 mol percent cobalt and 48 mol percent iron with the balance impurities, whose Curie point is 1253 K.; Vanadium Permendur, an alloy consisting essentially of 49 mol percent cobalt, 1.8 mol percent vanadium, and 46 mol percent iron, the balance impurities, whose Curie point is l253 K.; and Supermendur, an alloy consisting essentially of 49 mol percent cobalt, 2 mol percent vanadium, and 46 mol percent iron, the balance impurities, whose Curie point is also l253 K. Other magnetic materials possessing a relative permeability in excess of 5,000 gauss/oersted and a Curie point greater than l200 K. may also serve as the magnetic shielding 'of this invention. It may be noted that, where a magnetic electron emissive material is employed, the electron emitter 34 and the magnetic shielding of electrode 31 may form a homogeneous element in which the electrode is heated by resistances 33 or equivalent means.

The collector anode 41 consists essentially of a ferromagnetic material possessing the same characteristics as the magnetic shielding of the thermionic cathode 31. The anode may be composed of the same or a different magnetic material than the thermionic cathode but it is preferred that the same material be utilized.

Referring to FIGURES 4 and 5, the configuration of the magnetic field may be observed in the presence of (FIGURE 4) and in the absence of (FIGURE 5) the magnetic shielding of the present invention. In FIGURE 5, where electrodes 51 and 61 are each fabricated from non-magnetic conducting material, the lines of magnetic flux 56 extend generally parallel to the electrode surfaces 51, 61, thereby interfering with the reception by the electrodes of the random ion current and electron current produced by cathode 51. On the other hand, in the device of the invention illustrated in FIGURE 4, the provision of magnetic shielding on cathode 31 and the utilization of a magnetic material for collector anode 41 orients the magnetic field lines 46 normal to the electrode surfaces, thereby eliminating or minimizing the interference of the magnetic field with current production.

In operation, the ionized plasma particles are attracted toward the electrodes 31 and 41 and an electron flow is directed toward the collector anode from the electron emitter of cathode 31. The magnetic field configuration of FIGURE 4 serves to accelerate rather than to interfere with the collection upon the anode 41 and both the random ion current and electron current are available for useful electrical work.

The height of the electrodes is preferably the same as the height of the expansion chamber, but may be less, if desired. The length of the electrodes 31 and 41 is dependent upon the rate of flow, the temperature, the pressure, and the fractional ionization of the working fluid, and by the magnetic field intensity. The electrode length is that distance (in centimeters) which the electrodes extend in the direction of plasma flow. This length, of course, must be within practical limits. In general, electrode lengths of from 1 to 500 cm. are employed, lengths of from 5 to 100 cm. being preferred.

The equation defines the relationship between the length of the electrodes and the other factors hereinafter explained and included in this equation, which relationship, we have found, gives satisfactory efficiencies and outputs.

In this equation, D1 is a dimensionless distance or parameter determined from the plot in FIGURE 6 as the -ordinate value corresponding to the abscissa value for each Mach number M1 at the entrance of the magnetic field within the expansion chamber 17. D2 is a dimensionless distance or parameter determined from the plot in FIGURE 6 as the ordinate value corresponding to the abscissa value for each Mach number M2 at the exit end of the magnetic field.

As a practical matter, we have found that the value of D1D2 is within the range of from 0.2 to 10. Accordingly, the aforesaid relationship between the electrode length L and the said other factors may be expressed by the following equation:

In Equations 1 and 2 supra, a is the fractional ionization of the plasma, i.e., the ratio of the number of ions to the total number of neutral plasma particles per unit volume, Fy repersents the ratio of the specific `heats C/Cv of the flowing plasma, and (2b is the cyclotron frequency eB/m of the ions (secr-1). The parameter A is defined by the equation:

(2) )to2-n0 mi l/2 CZ"i 1/2 le 7ne) (Te) wherein mi and me are the mass of the flowing ions and the mass of the electrons, respectively, Ti and Te are the absolute temperatures of the ions and the electrons, respectively, and le and li represent the mean free paths of the electrons and the dissociated ions, respectively. The parameters NF, V* and 1,0* represent values of the collision frequency of the ions (seo-1), the gas velocity (cm/sec.) and the ratio of the cyclotron frequency to the collision frequency at a Mach number equal to unity, respectively. Lastly, Mav. is the average value -of the Mach number in the magnetic field r-egion.

A preferred embodiment of the apparatus depicted in FIGURES 1 and 3 includes an expansion chamber 17, having a cathode 31 whose walls comprise cobalt magnetic shielding encasing an electron emitter 34 composed of thoriated molybdenum and a collector anode 41 composed of cobalt magnetic material. Each of the electrodes extends a length of 18 cm. through the expansion chamber. A mercury vapor working fiuid is heated in the boiler 11 and enter nozzle 15 at the stagnation ternperature of 2,000 K. The iiuid is expanded through the nozzle and flows through the expansion chamber at a Mach number of 3.5. A power output of 21.2 watts per square cm. of cross-sectional area of iiow and a coefficient of performance of are produced.

The embodiments described above are intended to be illustrative and not restrictive of the present invention. Thus, instead of employing a closed cycle operation in which the working fluid is continually recycle, an open cycle system wherein an easily ionized substance such as cesium is introduced into a [combustion chamber and the hot exhaust gzses therefrom are then accelerated through a nozzle, passed through a magnetic field where their energy is converted to electric power, and then exhausted directly to the atmosphere, may be utilized. Combustible fuels such as oxygen, acetylene mixtures or the like can be burned to produce combustion chamber temperatures of the order of about 2,000 K. to 3,000 K. At such temperatures the introduction of about one percent of cesium into the chamber facilitates effective thermal ionization of the flowing gas in the order of about 0.01% to 0.1%, sufficient to produce useful electrical energy therefrom. The hot exhaust gases may be utilized to create further energy by exhaustion through a waste heat boiler to generate steam, or by operation of a turbine or other power generating equipment.

It will be noted that the present invention provides a novel process and apparatus for converting the energy of a plasma to electrical energy to produce :high current and power youtputs without loss due to magnetic field interference.

Since certain changes in carrying out the above process and in the plasma jet engine, which embody the invention, may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A process for producing electrical energy from the energy of a flowing plasma comprising: expanding a moving fluid into an expansion chamber having an appreciable extent in a direction along the path of flow of said fluid and having an electron emissive cathode provided with magnetic shielding, at least the outer surface of which shielding defining a portion of the path of flow of said moving fluid in said expansion chamber is constituted of a ferromagnetic material having a relative permeability in excess of 5,000 gauss/oersted and a Curie point greater than 1200 K., and lan electron receptive anode constituted of ferromagnetic material spaced from the magnetically shielded cathode across the path of flow of said moving fluid in said expansion chamber between said magnetically shielded cathode and said anode; ionizing said moving fluid to produce a plasma within said expansion chamber having a random ion current therein; heating said cathode to effect electron emission therefrom, thereby producing an electron current from said cathode through said plasma to said anode; creating a magnetic field within said expansion chamber having an appreciable extent along the path of flow of said plasma and the flux lines of said field, in the regions adjacent said cathode and said anode, extending toward said cathode and said anode with the flux lines nearest thereto extending substantially at right angles to, and into, the magnetic shielding on said cathode and the surface of said anode to deflect the ions within said plasma toward said magnetic shielding on said cathode and said anode and thus minimize interference between said magnetic field and the flow of said currents.

2. The process as defined in claim 1, in which a high frequency electric field ionizes said moving fluid to produce said plasma.

3. The process as defined in claim 2, in which said electric field has a frequency of from 100 kilocycles to 10,000 megacycles and is applied from a source external to the path of flow of said fluid.

4. A process for producing electrical energy from the energy of a flowing plasma comprising: isentropically expanding a moving ionizable fluid selected from the group consisting of the vapors of mercury, sodium, cesium,

lithium and potassium, said fluid having a temperature of from 900 to 3000 K. and a pressure of from 0.1 to 5 atmospheres, into an expansion chamber having an appreciable extent along the direction of the path of flow of said fluid and having an electron emissive cathode provided with magnetic shielding constituted of a ferromagnetic material having a relative permeability in excess of 5,000 gauss/oersted and a Curie point greater than 1200 K., and an electron receptive anode, constituted of a ferromagnetic material having a relative permeability in excess of 5,000 gauss/oersted and a Curie point greater than l200 K., disposed on opposite sides of the path of flow of said moving fluid; producing a high frequency electric field having a frequency of from kilocycles to 10,000 megacycles within said expansion chamber from a source external to the path of flow of the moving fluid to ionize said fluid `and produce a plasma within said expansion chamber having a random ion current therein; heating said cathode to effect electron emission therefrom, thereby producing an electron current from said cathode through said plasma to said anode; creating a magnetic field within said expansion chamber having an appreciable extent in the direction of flow of said plasma and having a field strength of from 5 103 gauss to 5 104 gauss, the lines of flux of said field, in the region adjacent said magnetic shielding on said cathode and said anode, extending toward said magnetic shielding on said cathode and said anode with the flux lines nearest thereto extending substantially at right angles to, and into, the surfaces of said magnetic shielding on said cathode and said anode to deflect the ions within said plasma toward said magnetic shielding on said cathode and said anode and thus minimize interference between said magnetic field and the flow of said currents.

5. An apparatus for producing electrical energy from the energy of a flowing plasma comprising, in combination, an expansion chamber having an appreciable length in the direction of ow of an ionizable fluid, nozzle means opening into one end of said expansion chamber through which said fluid is expanded into said expansion chamber for flow therethrough, means for creating a magnetic field within said expansion chamber extending along the length thereof, an electron emissive cathode in said expansion chamber, magnetic shielding covering at least the outer surface of said cathode, said magnetic shielding on the outer surface of said cathode defining a portion of the path of flow of said ionizable fluid through said expansion chamber and constituted of a ferromagnetic material having `a relative permeability greater than 5,000 gauss/oersted and a Curie point greater than l200 K., a ferromagnetic electron receptive anode spaced from said magnetic shielding on at least the `outer surface of said cathode, between which anode and said magnetic shielding ionizable fluid flows in said expansion chamber, means for ionizing said fluid to produce an ionized plasma having a random ion current therein, and means for heating said cathode to produce an electron current adapted to pass from said cathode through said plasma to said anode.

6. The apparatus as defined in claim 5 in which said cathode consists essentially of an electron emitter of the group consisting of thoriated tungsten and thoriated molybdenum and said magnetic shielding is a housing for said cathode, which housing is constituted of said ferromagnetic material having a relative permeability greater than 5,000 gauss/oersted and a Curie point greater than 1200 K.

7. The apparatus as defined in claim 5, in which the means for ionizing said fluid is positioned adjacent the outer sides of said expansion chamber near the opposite ends thereof and is energized by a high frequency power source for producing a high frequency electric field within said expansion chamber extending along the length thereof.

10 8. The apparatus as deined in claim 5, in which said References Cited by the Examiner cathode and said anode are plate-like electrodes extending UNITED STATES PATENTS substantially throughout the length of sald magnetlc eld,

cobalt, 1.8 mol percent vanadium and 46 mol percent iron, and an -alloy consisting essentially of 49 mol percent cobalt, 2 mol percent vanadium and 46 mol percent iron. 10

MILTON O. HIRSHFIELD, Primary Examiner. 

1. A PROCESS FOR PRODUCING ELECTRICAL ENERGY FROM THE ENERGY OF A FLOWING PLASMA COMPRISING: EXPANDING A MOVING FLUID INTO AN EXPANSION CHAMBER AHVING AN APPRECIABLE EXTENT IN A DIRECTION ALONG HE PATH OF FLOW OF SAID FLUID AND HAVING AN ELECTRON EMISSIVE CATHODE PROVIDED WITH MAGNETIC SHIELDING, AT LEAST THE OUTER SURFACE OF WHICH SHIELDING DEFINING A PORTION OF THE PATH OF FLOW OF SAID MOVING FLUID ON SAID EXPANSION CHAMBER IS CONSTITUTED OF A FERROMAGNETIC MATERIAL HAVING A RELATIVE PERMEABILITY IN EXCESS OF 5,000 GAUSS/ORESTED AND A CURIE POINT GREATER THAN 1200*K., AND AN ELECTRON RECEPITVE ANODE CONSTITUTED OF FERROMAGNETIC MATERIAL SPACED FROM THE MAGNETICALLY SHIELDED CATHODE ACROSS THE PATH OF FLOW OF SAID MOVING FLUID IN SAID EXPANSION CHAMBER BETWEEN SAID MAGNETICALLY SHIELDED CATHODE AND SAID ANODE; IONIZING SAID MOVING FLUID TO PRODUCE A PLASMA WITHIN SAID EXPANSION CHAMBER HAVING A RANDOM ION CURRENT THEREIN; HEATING SAID CATHODE TO EFFECT ELECTRON EMISSION THEREFROM, THEREBY PRODUCING AN ELECTRON CURRENT FROM SAID CATHODE THROUGH SAID PLASMA TO SAID ANODE; CREATING A MAGNETIC FIELD WITHIN SAID EXPANSION CHAMBER HAVING AN APPRECIABLE EXTENT ALONG THE PATH OF FLOW OF SAID PLASMA AND THE FLUX LINES OF SAID FIELD, IN THE REGIONS ADJACENT SAID CATHODE AND SAID ANODE, EXTENDING TOWARD SAID CATHODE AND SAID ANODE WITH THE FLUX LINES NEAREST THERETO EXTENDING SUBSTANTIALLY AT RIGHT ANGLES TO, AND INTO, THE MAGNETIC SHIELDING ON SAID CATHODE AND THE SURFACE OF SAID ANODE TO DEFLECT THE IONS WITHIN SAID PLASMA TOWARD SAID MAGNETIC SHEIDLING ON SAID CATHODE AND SAID ANODE AND THUS MINIMIZE INTERFERENCE BETWEEN SAID MAGNETIC FIELD AND THE FLOW OF SAID CURRENTS. 